1) It's a play on the word "Energy."
2) Mechanically, similar to GotP. Thematically, energy doesn't disappear (disregard Einstein's theory please), but turns into different forms.
3) Well, that only causes problems with SoSa...unless that runs on a different system.
4) The first copy doesn't deal damage, but each other copy you play will. You most likely will play more copies, because this type of card is a type that will benefit you from having multiple copies.
5) More than mass, acceleration, or anything physics related, I view Gravity as the element of absolute law (look at Gravity Shield, or Momentum). The "law" here, is that quanta spent will deal damage.